static int zhuffman_decode_slowpath(zbuf a, zhuffman z)
{
int b, s, k;
// not resolved by fast table, so compute it the slow way
// use jpeg approach, which requires MSbits at top
k = bit_reverse((int)a.code_buffer, 16);
for (s = ZFAST_BITS + 1; ; ++s)
{
if (k < z.maxcode[s])
{
break;
}
}
if (s == 16)
{
return(-1); // invalid code!
}
// code size is s, so:
b = (k >> (16 - s)) - z.firstcode[s] + z.firstsymbol[s];
Debug.Assert(z.size[b] == s);
a.code_buffer >>= s;
a.num_bits -= s;
return(z.value[b]);
}
static int zbuild_huffman(zhuffman z, byte[] sizelist, int num, int sizelistOffset = 0)
{
int i, k = 0;
int code; int[] next_code = new int[16]; int[] sizes = new int[17];
// DEFLATE spec for generating codes
Array.Clear(z.fast, 0, z.fast.Length);
for (i = 0; i < num; ++i)
{
++sizes[sizelist[i + sizelistOffset]];
}
sizes[0] = 0;
for (i = 1; i < 16; ++i)
{
Debug.Assert(sizes[i] <= (1 << i));
}
code = 0;
for (i = 1; i < 16; ++i)
{
next_code[i] = code;
z.firstcode[i] = (ushort)code;
z.firstsymbol[i] = (ushort)k;
code = (code + sizes[i]);
if (sizes[i] != 0)
{
if (code - 1 >= (1 << i))
{
throw new Exception("bad codelengths,Corrupt JPEG");
}
}
z.maxcode[i] = code << (16 - i); // preshift for inner loop
code <<= 1;
k += sizes[i];
}
z.maxcode[16] = 0x10000; // sentinel
for (i = 0; i < num; ++i)
{
int s = sizelist[i + sizelistOffset];
if (s != 0)
{
int c = next_code[s] - z.firstcode[s] + z.firstsymbol[s];
ushort fastv = (ushort)((s << 9) | i);
z.size[c] = (byte)s;
z.value[c] = (ushort)i;
if (s <= ZFAST_BITS)
{
int kk = bit_reverse(next_code[s], s);
while (kk < (1 << ZFAST_BITS))
{
z.fast[kk] = fastv;
kk += (1 << s);
}
}
++next_code[s];
}
}
return(1);
}
static int compute_huffman_codes(zbuf a)
{
zhuffman z_codelength = new zhuffman();
byte[] lencodes = new byte[286 + 32 + 137];//padding for maximum single op
byte[] codelength_sizes = new byte[19];
int i, n;
int hlit = (int)zreceive(a, 5) + 257;
int hdist = (int)zreceive(a, 5) + 1;
int hclen = (int)zreceive(a, 4) + 4;
for (i = 0; i < hclen; ++i)
{
int s = (int)zreceive(a, 3);
codelength_sizes[length_dezigzag[i]] = (byte)s;
}
if (zbuild_huffman(z_codelength, codelength_sizes, 19) == 0) return 0;
n = 0;
while (n < hlit + hdist)
{
int c = zhuffman_decode(a, z_codelength);
Debug.Assert(c >= 0 && c < 19);
if (c < 16)
lencodes[n++] = (byte)c;
else if (c == 16)
{
c = (int)zreceive(a, 2) + 3;
{
byte value = lencodes[n - 1];
int last = n + c;
for (int idx = n; idx < last; idx++)
lencodes[idx] = value;
}
n += c;
}
else if (c == 17)
{
c = (int)zreceive(a, 3) + 3;
Array.Clear(lencodes, n, c);
n += c;
}
else
{
Debug.Assert(c == 18);
c = (int)zreceive(a, 7) + 11;
Array.Clear(lencodes, n, c);
n += c;
}
}
if (n != hlit + hdist) throw new Exception("bad codelengths,Corrupt PNG");
if (zbuild_huffman(a.z_length, lencodes, hlit) == 0) return 0;
if (zbuild_huffman(a.z_distance, lencodes, hdist, hlit) == 0) return 0;
return 1;
}
static int zhuffman_decode(zbuf a, zhuffman z)
{
int b, s;
if (a.num_bits < 16)
{
fill_bits(a);
}
b = z.fast[a.code_buffer & ZFAST_MASK];
if (b != 0)
{
s = b >> 9;
a.code_buffer >>= s;
a.num_bits -= s;
return(b & 511);
}
return(zhuffman_decode_slowpath(a, z));
}
static int zhuffman_decode_slowpath(zbuf a, zhuffman z)
{
int b, s, k;
// not resolved by fast table, so compute it the slow way
// use jpeg approach, which requires MSbits at top
k = bit_reverse((int)a.code_buffer, 16);
for (s = ZFAST_BITS + 1; ; ++s)
if (k < z.maxcode[s])
break;
if (s == 16) return -1; // invalid code!
// code size is s, so:
b = (k >> (16 - s)) - z.firstcode[s] + z.firstsymbol[s];
Debug.Assert(z.size[b] == s);
a.code_buffer >>= s;
a.num_bits -= s;
return z.value[b];
}
static int zhuffman_decode(zbuf a, zhuffman z)
{
int b, s;
if (a.num_bits < 16) fill_bits(a);
b = z.fast[a.code_buffer & ZFAST_MASK];
if (b != 0)
{
s = b >> 9;
a.code_buffer >>= s;
a.num_bits -= s;
return b & 511;
}
return zhuffman_decode_slowpath(a, z);
}
static int zbuild_huffman(zhuffman z, byte[] sizelist, int num, int sizelistOffset = 0)
{
int i, k = 0;
int code; int[] next_code = new int[16]; int[] sizes = new int[17];
// DEFLATE spec for generating codes
Array.Clear(z.fast, 0, z.fast.Length);
for (i = 0; i < num; ++i)
++sizes[sizelist[i + sizelistOffset]];
sizes[0] = 0;
for (i = 1; i < 16; ++i)
Debug.Assert(sizes[i] <= (1 << i));
code = 0;
for (i = 1; i < 16; ++i)
{
next_code[i] = code;
z.firstcode[i] = (ushort)code;
z.firstsymbol[i] = (ushort)k;
code = (code + sizes[i]);
if (sizes[i] != 0)
if (code - 1 >= (1 << i)) throw new Exception("bad codelengths,Corrupt JPEG");
z.maxcode[i] = code << (16 - i); // preshift for inner loop
code <<= 1;
k += sizes[i];
}
z.maxcode[16] = 0x10000; // sentinel
for (i = 0; i < num; ++i)
{
int s = sizelist[i + sizelistOffset];
if (s != 0)
{
int c = next_code[s] - z.firstcode[s] + z.firstsymbol[s];
ushort fastv = (ushort)((s << 9) | i);
z.size[c] = (byte)s;
z.value[c] = (ushort)i;
if (s <= ZFAST_BITS)
{
int kk = bit_reverse(next_code[s], s);
while (kk < (1 << ZFAST_BITS))
{
z.fast[kk] = fastv;
kk += (1 << s);
}
}
++next_code[s];
}
}
return 1;
}
static int compute_huffman_codes(zbuf a)
{
zhuffman z_codelength = new zhuffman();
byte[] lencodes = new byte[286 + 32 + 137];//padding for maximum single op
byte[] codelength_sizes = new byte[19];
int i, n;
int hlit = (int)zreceive(a, 5) + 257;
int hdist = (int)zreceive(a, 5) + 1;
int hclen = (int)zreceive(a, 4) + 4;
for (i = 0; i < hclen; ++i)
{
int s = (int)zreceive(a, 3);
codelength_sizes[length_dezigzag[i]] = (byte)s;
}
if (zbuild_huffman(z_codelength, codelength_sizes, 19) == 0)
{
return(0);
}
n = 0;
while (n < hlit + hdist)
{
int c = zhuffman_decode(a, z_codelength);
Debug.Assert(c >= 0 && c < 19);
if (c < 16)
{
lencodes[n++] = (byte)c;
}
else if (c == 16)
{
c = (int)zreceive(a, 2) + 3;
{
byte value = lencodes[n - 1];
int last = n + c;
for (int idx = n; idx < last; idx++)
{
lencodes[idx] = value;
}
}
n += c;
}
else if (c == 17)
{
c = (int)zreceive(a, 3) + 3;
Array.Clear(lencodes, n, c);
n += c;
}
else
{
Debug.Assert(c == 18);
c = (int)zreceive(a, 7) + 11;
Array.Clear(lencodes, n, c);
n += c;
}
}
if (n != hlit + hdist)
{
throw new Exception("bad codelengths,Corrupt PNG");
}
if (zbuild_huffman(a.z_length, lencodes, hlit) == 0)
{
return(0);
}
if (zbuild_huffman(a.z_distance, lencodes, hdist, hlit) == 0)
{
return(0);
}
return(1);
}
